Photoconductor overcoat consisting of nano metal oxide particles, urethane resin, crosslinkable siloxaines, acrylic copolymer and no transport materials

Abstract

An improved overcoat layer for an organic photoconductor drum of an electrophotographic image forming device is provided. The overcoat layer is prepared from a curable composition including a crosslinkable siloxane, an acrylic polymer with pigment affinic groups, nano metal oxide particles sized less than 400 nm in combination with a urethane acrylate resin having at least 6 functional groups. The outermost layer of an organic photoconductors is coated with the overcoat formulation of the present invention then cured. The resulting cured overcoated organic photoconductor has improved wear resistance and importantly does not negatively altering the electrophotographic properties of the organic photoconductor.

What is claimed is: 
     
         1 . A method of preparing an organic photoconductor drum comprising:
 providing an electrically conductive substrate;   preparing a charge generation layer dispersion:   coating the charge generation layer dispersion over the electrically conductive substrate to form a charge generation layer;   preparing a charge transport layer dispersion;   coating the charge transport layer dispersion over the charge generation layer to form a charge transport layer;   preparing an overcoat layer formulation including: 
 about 20 percent to about 95 percent by weight of a urethane acrylate resin having at least six radical polymerizable functional groups; 
 about 5 percent to about 30 percent by weight of a nano metal oxide particle sized less than 400 nm and selected from the group consisting of indium tin oxide, aluminum oxide, zirconium oxide, zinc oxide, indium oxide, lanthanum oxide and antimony tin oxide; 
 about 0.05 percent to about 3 percent by weight of a crosslinkable siloxane; 
 about 0.05 percent to about 6 percent by weight of a structured acrylic polymer with pigment affinic groups; and 
 an organic solvent; 
   coating the overcoat layer formulation over the charge transport layer; and   curing the overcoat layer formulation to form a photoconductor having an overcoat layer over the charge transport layer and the charge generation layers, wherein the overcoat layer does not include charge transport materials.   
     
     
         2 . The method of  claim 1 , wherein the urethane acrylate resin having at least six radical polymerizable functional groups is a hexa-functional aromatic urethane acrylate resin having the following structure:
                       .   
     
     
         3 . The method of  claim 1 , wherein the urethane resin having at least six radical polymerizable functional groups is a hexa-functional aliphatic urethane acrylate resin having the following structure:
                       .   
     
     
         4 . The method of  claim 1 , wherein the overcoat layer is cured by an electron beam. 
     
     
         5 . The method of  claim 4 , wherein the cured overcoat layer has a thickness of about 1.5 µm. 
     
     
         6 . The method of  claim 1 , wherein the nano metal oxide particle is indium tin oxide. 
     
     
         7 . The method of  claim 6 , wherein the indium tin oxide is sized less than 200 nm. 
     
     
         8 . The method of  claim 1 , wherein the crosslinkable siloxane is crosslinkable polyether modified acryl functional polymethylsiloxane. 
     
     
         9 . The method of  claim 1 , wherein the overcoat layer formulation further includes a coating aid additive. 
     
     
         10 . The method of  claim 9 , wherein the amount of the coating aid additive is about 0.1 to about 5 percent by weight of the curable composition.